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27 October 2016 Female-biased sexual size dimorphism: ontogeny, seasonality, and fecundity of the cliff chipmunk (Tamias dorsalis)
Allyssa L. Kilanowski, John L. Koprowski
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Abstract

Female-biased sexual dimorphism is uncommon in mammals and is usually attributed to increased fecundity of large females. Moreover, sexual dimorphism is usually described for adults, and the ontogeny of sex differences is poorly documented. We studied cliff chipmunks (Tamias dorsalis), a small mammal with female-biased sexual dimorphism, to describe development of sexual dimorphism in juveniles and to measure sexual dimorphism and seasonal body mass in adults. To test the fecundity hypothesis, we compared body mass of females to litter size and body mass of offspring. Juveniles were not sexually dimorphic at emergence from the nest and did not differ in body mass 2 months after emergence. Adult chipmunks maintained a relatively stable body mass in March– October with females consistently larger than males. Maternal mass did not have an effect on litter size or mass of juveniles. Because females were consistently larger than males, the ontogeny of sexual dimorphism may provide insights into selection pressures that lead to female-biased sexual dimorphism.

© 2016 American Society of Mammalogists, www.mammalogy.org
Allyssa L. Kilanowski and John L. Koprowski "Female-biased sexual size dimorphism: ontogeny, seasonality, and fecundity of the cliff chipmunk (Tamias dorsalis)," Journal of Mammalogy 98(1), 204-210, (27 October 2016). https://doi.org/10.1093/jmammal/gyw172
Received: 23 December 2015; Accepted: 4 October 2016; Published: 27 October 2016
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